1. Field of the Invention
The invention relates to a piston pump for a vehicle brake system, having a housing portion and a piston that is dispiaceably guided in the housing portion and has an inlet valve with a sealing seat embodied on the piston.
2. Description of the Prior Art
The piston pumps used for known vehicle brake systems, particularly anti-lock brake systems (ABS), serve to control the pressure in wheel brake cylinders. In the ABS, the piston pumps are provided for instance for returning brake fluid from one or more wheel brake cylinders to a master cylinder. The ABS often functions in combination with traction control (TC). Another known system, called an electronic stability program (ESP), improves driving safety by a further increment compared to ABS and TC. Wile ABS and TC function in the longitudinal direction of travel, ESP has an influence on transverse dynamics and therefore in principle is transverse traction control. For all these systems as well a further systems for increasing driving safety, piston pumps are employed.
Known piston pumps provided for vehicle brake systems comprise among other components a cylinder, which is embodied in a housing and in which a piston is received longitudinally movably. The piston drive is usually effected via an eccentric element, at which the rotary motion of a shaft driven by means of an electric motor is converted into a translational motion of a piston rod of the piston. The piston rod is pressed with its face end against the outer circumference of the eccentric element by means of a prestressing element, for instance in the form of a helical spring. Thus in the final analysis, a reciprocating pumping motion of the piston can be attained.
Known piston pumps furthermore as a rule have an inlet valve embodied as a seat valve, for controlling the inflow of fluid. The inflow of fluid from outside the piston pump through the inlet valve is effected in known piston pumps via a suction line, which has a comparatively high flow resistance. As a consequence, known piston pumps used for vehicle brake systems do not have sufficiently effective pressure buildup dynamics, since because of the high flow resistance, they can be filled only relatively slowly.
It is the object of the invention to create a piston pump of the type defined at the outset, in which the aforementioned problems are overcome and which have high pressure buildup dynamics.